1. Field of the Invention
The present invention relates to a surround signal processing apparatus, and more particularly, to a surround signal processing apparatus and method which can realize sound image localization and have reverberation effects.
2. Prior Art
Conventionally, when stereophonic sound is reproduced in such a way as to provide a sound field expanding behind a listener or to localize a sound image behind a listener, two front speakers are arranged in front of a listener for stereophonic sound reproduction and at least one or two rear speaker are additionally arranged behind the listener for surround sound reproduction; in other words, at least three speakers must be arranged at the minimum around a listener. Further, in the case where surround sound is reproduced on the basis of a one-system surround signal or a center channel is additionally required to be reproduced as with the case of the 3-1 system of high vision high definition TV(HDTV), one or two additional center speakers must be arranged. Therefore, amplifiers and cables corresponding to the numbers of the reproduced channels are necessary.
U.S. Pat. No. 5,572,591, (issued to Hiroko Numazu et al. on Nov. 5, 1996) discloses a sound field controller for reproducing sound effects for use in audio equipment or in audio-visual(AV) equipment.
FIGS. 1 and 2 are views for showing conventional surround signal processors. As shown in FIG. 1 for instance, in the case of the surround sound reproduction, it has been necessary to arrange two front L(left)- and R(right)-channel speaker sets for stereophonic sound on front left and right sides of a listener LM, two rear SL(surround left)- and SR(surround right)-channel speaker sets for surround sound on rear left and right sides thereof, and further a C(center)-channel speaker at the front middle thereof, respectively.
However, since it is difficult to arrange the two rear speakers and the center speaker from the standpoint of space and cost, in homes or vehicles, as shown in FIG. 2, only L- and R-channel speakers are installed on the front left and right sides of a listener LM in practice. In this speaker arrangement, it has become impossible to obtain sufficient surround sound effect. In the case of the surround reproduction system using a monophonic surround signal in particular, although this system has such a feature that a sound field can be obtained on the rear side of a listener or the sound image can be shifted, it has been impossible to obtain such effects as described above without arranging the rear speakers.
Therefore, it is an object of the present invention, for the purpose of solving the above mentioned problems, to provide a surround signal processing apparatus and method which can realize sound image localization and have reverberation effects.
In order to attain the object, according to the present invention, there is provided a surround signal processing apparatus, said apparatus comprising:
left and right impulse measuring sections for measuring left and right impulses of a head related transfer function for an input audio signal based on a number of a plurality of lattices defined in a three dimensional space, horizontal and vertical angles defined by a center of a dummy head and the plurality of lattices;
left and right convolution operators for convolving left and right channel signals of the input audio signal with the left and right impulses of the head related transfer function from the left and right impulse measuring sections, respectively, in order to localize sound image for the input audio signal at an objective localization position in the three-dimension space; and
left and right reverberators for imparting first and second reverberant sounds to the left and right channel signals of the input audio signal from the left and right convolution operators, respectively.
Also, the present invention provides a surround signal processing method, said method comprising the steps of:
(a) measuring left and right impulses of a head related transfer function for an input audio signal based on a number of a plurality of lattices defined in a three dimensional space, horizontal and vertical angles defined by a center of the three dimensional space and the plurality of lattices;
(b) convolving left and right side signals of the input audio signal with the left and right impulses of the head related transfer function measured in step (a), respectively, in order to localize sound image for the input audio signal at an objective localization position in the three dimensional space; and
(c) imparting first and second reverberant sounds to the left and right side signals of the input audio signal, respectively.
According to the present invention, it is possible to localize the sound images of the surround signals at two different rear positions apart from the two front positions at which a pair of speakers are arranged, on the basis of the sound signals reproduced through speakers. The present invention also provides a listener with a feeling of presence as if he is listening to the music in a different sound field such as a spacious concert hall, church or stadium notwithstanding the fact that he is actually in an ordinary room, a listening room, or a vehicle.
Other objects and further features of the present invention will become apparent from the detailed description when read in conjunction with the attached drawings.